REVERSAL OF SEX-ROLES IN THE COPULATORY-BEHAVIOR OF THE IMPORTED CRAYFISH PROCAMBARUS-CLARKII

Copulatory behavior of the crayfish Procambarus clarkii was observed i n the laboratory. This behavior was asymmetrical, in that the male mou nted the female and grasped her chelipeds with his chela. Crayfish in various combinations (1 female and 1 male, 1 female and 2 males, and 2 females and 1 male) were confined in an aquarium and observed. The nu mber of copulations, the number of copulation attempts by males, total duration of copulations, and the average duration of a copulation wer e not different among the 3 combinations. Females initiated behavior s imilar to the copulatory behavior initiated by males only in experimen ts with 2 females and 1 male. The frequency of this reversed copulator y behavior was greater in the experiments with 2 females and 1 male th an it was with the other 2 combinations.